Sheet and bag folder

ABSTRACT

A machine which imparts four folds to flattened plastic refuse bags and the like is characterized by a plurality of adjacent feed stations to which the bags are fed simultaneously and from each of which station the bag receives two folds; and a transport system which includes a mechanical time delay, which feeds the double-folded bags in series to a single station from which two additional folds are imparted. The mechanism for each fold comprises an air knife having a uniform pressure profile along the length of its air gap in combination with a pair of rollers having fixed and floating bearings, respectively.

Umted States Patent 11 1 1111 3,773,315 Tsien Nov. 20, 1973 SHEET AND BAG FOLDER Primary Examiner-Robert W. Michell Assistant ExaminerA. Heinz 75 I t H C.T L t ,NJ. 1 men or sue slen lvmgs on Attorney-Manahan & Wohlers, F. Donald Paris and [73] Assignee: Esso Research and Engineering Ch l A C h Company, Linden, NJ.

[22 Filed: June 4, 1971 [57] ABSTRACT A machine which imparts four folds to flattened plasl Appl' 150099 tic refuse bags and the like is characterized by a plurality of adjacent feed stations to which the bags are [52] us. c1. 270/69 fed Simultaneously and from each of which station the 51 1111. C1 B65h 45/00 bag receives twc folds; and a transport System which [58 Field of Search 270/69; 226/97 includes a mechanical time delay, which feeds the double-folded bags in series to a single station from 5 R f r Cited which two additional folds are imparted. The mecha- UNITED STATES PATENTS nism for each fold comprises an air knife having a uniform pressure profile along the length of its air gap in 3 3 2 combination with a pair of rollers having fixed and 22016539 10 1935 Brenn 270/61 F flatmg beamgs' respecnvely' 4 Claims, 11 Drawing Figures FIELD OF THE INVENTION PRIOR ART Refuse bags made from thermoplastic polyolefin tubing have received wide consumer and governmental acceptance as convenient and economical containers for the disposal of garbage, lawn sweepings and the like. Commonly the bags are made from polyolefins such as polyethylene and polypropylene or from plasticized polyvinyl chloride tubing having a circumference of 60 inches (1,524 cm) in a length of 37 inches (940 cm), heat sealed at one end. In order for the bag to conform more readily to the standard gallon (75.7 liters) garbage receptacle having a diameter of 18.5 inches (47 cm), it has been the practice to fabricate the bags with -two lengthwise accordion pleats or gussets, folded so .that each vee (V) has two 7 inch (17.8 cm) legs lying between two 16 inch (40.6 cm) faces.

For packaging to the ultimate consumer, hand folding has largely been used due to the fragile nature of the film which has a thickness in the range of 0.5 to 1.5 mils (0.0l27 mm to 0.0381 mm). Attempts to use mechanical folders of the type used for folding textile sheeting or newsprint has met with indifferent success due to the relatively low speed at which theyoperate and the tendency for these machines to introduce pinholes or tears in the film.

Recently, a number of machines for folding refuse bags have become available, but they have practical limitations for full commerical acceptability. In one type of machine which folds the bag only twice, the fold is accomplished by a mechanical chop-tucking" blade which descends across the bag and tucks the partially folded bag between moving belts which-complete the fold.

Another type of machine uses the same moving belt arrangement for completing the fold, folding the bag three times, but replaces the mechanical blade with a perforated pipe through which a blast of air initiates the tuck into the belts. Both machines suffer from a limitation in folding capacity, producing bags having a high bulk which require sizes of packages which are uneconomical to manufacture and occupy a large amount of shelf space in marketing outlets. In addition, the second machine has a tendency to yield a fold which is skewed due to the variable pressure profile of the air-blast issuing from the perforated pipe.

SUMMARY OF THE INVENTION This invention relates to a machine for imparting two transverse or cross folds, followed by two longitudinal or lengthwise folds to sheets, bags and the like articles made from plastics, paper or textiles. The machine comprises a plurality of feed stations to which, for example, plastic refuse -bags are fed simultaneously in parallel lines and from which the bag receives two cross folds, and a transport system with mechanical delay for feeding the double-folded bags in series to a single station from which the bags receive two lengthwise folds and are stacked'in readiness for packaging.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view of the bag-folding machine equipped with two feed stations. Unfolded bags 101A and 1018 are shown in position in guiding trays 3A and 38 just prior to the start of the folding operation.

FIGS. 2, 4, 5, 6 and 7 are sectional views in elevation of the machine illustrated in FIG. I at indiciahaving the same numbers as the corresponding figures.

FIG. 3a shows the bag, 10] beginning the first crossfold 102.

FIG. 3b shows the once folded bag [03, beginning the second cross-fold 104.

FIG. 30 shows the bag folded twice, 105.

FIG. 8 is a quarter sectional view through a floating roller.

FIG. 9 is a block diagram illustrating the electronics used for timing the sequence of the folds.

DETAILED DESCRIPTION OF DRAWINGS Referring to FIGS. 1 and 2, unfolded bags 101A and 1018 delivered to the forward end 240 of first feed trays 3A and 38 toward rearward end 242 of said trays, sized to accommodate the unfolded bags from bag making machines (not shown), actuate first photo cell receptors 2A and 28 by interruption and restoration of light passing through the light-slots 130A and 1308 in distal tray 3A and proximal tray 38 respectively from first photo cell light sources 1A and 18 through suitable electronic circuitry to trigger open solenoid valves 5A and S8 to admit air under pressure to the first-fold air-knives 4A and 4B. Air-knives 4A and 48, shown in front elevation in FIG. 4, are equipped with pressure equalizing slugs 6 threaded into the sides of the airknives 4A and 48 so as to permit tuning of the airknives to give a uniform pressure distribution profile along the entire length of the knives. Without the equalizing slugs 6, which create a turbulent flow in the interior of the knife, the knives exhibit a Coanda effeet in which the air preferentially goes to one side or the other, creating a non-uniform pressure-profile along the length of the knife opening. Tuning of the airknives by greater or less insertion of the threaded equalizing slugs so as to produce a uniform pressureprofile along the length of the knife may be readily accomplished with the aid of any convenient pressuresensitive transducer such as a crystal microphone connected to a memory-type oscilloscope or the like. Failure to have a uniform pressure along the length of the knife causes skewing of the fold with the formation of a commercially unattractive product.

The air blast from the first air-knives 4A and 4B which is of 20 milliseconds to 60 milliseconds duration pushes the unfolded bags 101A and 101B downwardly through the openings or slots located approximately midway in feed trays 3A and 38 to begin first fold 102 and be caught between the first fixed top roller 7, revolving on shaft 8, journaled in fixed bearings attached to superstructure 75, and first floating roller 9, revolving on shaft 10, journaled in floating bearings 27. First fixed top roller 7 and first floating roller 9 are in tangential contact with a plane passing through air-knives 4A and 4B and slots 90; Bearings 27, shown in greater detail in FIG. 7 are slidably fitted in ways 110, attached to superstructure 75, so as to permit slidable movement of floating roller 9, to and from fixed roller 7,-while biased toward fixed roller 7 by compression springs 28.

Passage of the bag between rollers 7 and 9, which are fabricated from an elastomeric composition having a Shore A hardness within the limits of 25 to 40, preferably 30 to 35 as determined by Durometer under the conditions specified by ASTM test method D-676,

completes the first fold and places the once-foldedbag 103, in position for the second fold.

. Initiation of the second fold 104, is by an air'blast from a pair of air-knives 24A and 24B of which 24A is illustrated in FIG. 2 Air-knives 24A and 24B are similar in all respects to air-knives 4A and 4B and include tuneable slugs 26 and solenoid valves 25A and 253 for admitting air under pressure to the respective airknives.

Actuation of solenoids 5A, 5B; and 24A and 24B for the first and second folds respectively is controlled by conventional electronic circuitry a block diagram of which is illustrated in FIG. 9, comprising a light actuated pulse generator 132 having an adjustable pulse width in the range of 20 to 60 milliseconds which drives solenoid drive 134 controlling solenoids 5A and 5B; and a uni-junction transistor flip-flop adjustable timedelay 136 driven by the pulse generator 132, driving in its turn a uni-junction transistor solenoid driver 138 for controlling solenoids 25A and 258.

The time-delay is adjusted so that solenoid valves 25A and 258 open at a time when the once-folded bags 103 reach their midpoint opposite air-knives 24A and 248. The air blast, from air-knives 24A and 24B, pushes the once-folded bags between the first floating roller 9 and first fixed bottom roller 1 1 to begin the second fold 104. The first fixed bottom roller 11, revolves on shaft 12 which is journaled in fixed bearings supported by superstructure 75. Guard plate 29, which is electrically grounded, follows at its upper end the curvature of first fixed bottom roller 11, and removes any static charge acquired by the once-folded bag 103, and prevents accidental adherence of the bag to the rollers or wrapping of the bag around roller 11. Roller 11 is fabricated from an elastomeric composition having the ame characteristics as roller 7.

First floating roller 9, shown in quarter-section in FIG. 8, has a plurality of grooves53, in which endless clamping belts 13, are set and revolve on pulleys 15, carried on upper counter-shaft 16, which isjoumaled in slidable bearings 62, carried by adjustable gibs and ways I20, attached to superstructure 75. Between grooves 53, which may be made by grinding roller 9, are strips of foamed tape 128 attached to the surface of roller 9. Foamed tape 128 which may comprise an elastomer or plastic such as an open-celled polyurethane is an essential feature to the successful operation of the machine. Suitable tape will have a density in :the range of 0.6 to 30 pounds per cubic foot and a com pressive strength at percent deflection of 0:2 to 4 P.S.I. at 25 percent. A polyurethane tape available commercially as No. 4,308 made by the 3M Company has been found to be suitable, The foamed tape prevents the formation of a vacuum seal between the bag and roller 9 and eliminates the tendency of the bag to adhere to the roller or to whiplash due to the springlike action of the tape. I 1 H In order to maintain clamping belts 13 taut during the momentary interval that the bags pass between rollers 7 and 9, and 9Ya nd"ll,-'bearings '62Icarrying countershaft 16 are biased by compression spring 58.

First fixed bottom roller 1 1 has a plurality of grooves 85, corresponding in number and in vertical alig nment with grooves 53', inwhich endlesssupporting belts 14 are set and revolve on-"pulleys l7, carr ied on lower countershaft 18, Whi'tlh is joumaled infixed-bearings attached to superstructure 75. First floating roller 9 is in'tangential contact with first fixed top roller 7 and first fixedbottorn roller 11, and all the rollers are aligned inpai'allelwith slots"""90"'in trays 3A and 3B and air-knives, 4A and 4B in order to minimize skewing of the folds.

As a blast of "air from air-knives 24A and 24B force the once-folded bags between the first floating roller 9, and the first fixed bottom roller ll, the second fold is completed by passage of the bags between these rollers. The twice-folded bags are then carried between supporting belts 14, and clamping belts 13 over guiding slide 19 and under deflectorplate 20 onto the crossconveyor belt 22. A retarding plate 21, used only with bags from station 3A is movable toward or away from third-fold guidingtray 33, and acts as a mechanical time delay by varying the time duration of the surface contact of the bag with conveyor belt 22, so that twicefolded bags 1058 and 105A may receive their third folds in series with sufficient spacing between the bags.

FIG. 4 is a view of the rear of the machine in elevation showing twice-folded bag 105B on conveyor belt 22 and twice-folded bag 105A lying partially on retarding plate 21 and on conveyor belt 22 just prior to both being conveyed in series to second feed tray 33. Also illustrated is a twice-folded bag 105, in feed tray 33 just prior to the beginning of the third and fourth folds, terminating as a four-folded bag 106, in receiving tray 1 I5.

Conveyor belt 22 is supported by drive roller 60, revolving on shaft 59, and driven roller 61, revolving on shaft 23. Shafts 59 and 23 are journaled in bearings attached to superstructure 75, and the bearing blocks joumaling shaft 23 are supplied with conventional tension screws so as to maintain the conveyor belt taut and in alignment.

Twice-folded bags 1058 and 205A are moved on conveyor belt 22 to the leading edge of second guide tray 33 and assisted onto the tray by a blast of air directed downwardly and outwardly toward tray 33 from air-holes 43 in air pusher tube 30. As the twice-folded bag 105 passes light-slot 70 in second guide tray 33, a beam of light from light source 31 impinging on photocell 32 is momentarily interrupted. Restoration of the light from light source 31 triggers pulse generator 140 to actuate solenoid driver 144 to open solenoid 35 to admit air'under pressure to third-fold air knife 34.

Means foneffectuating the third and fourth folds are similar to the means used for the first and second folds and include: third-fold air knife 34 having tuneable slugs 36 and solenoid 35; second fixed top roller 37 mounted on shaft 38 journaled in fixed bearings attached to superstructure second floating roller 39 having a plurality of grooves 57, mounted on shaft 40, journaled in bearing blocks 47 slidably mounted and biased by compression springs 48 in ways attached to superstructure 75; fourth-fold air-knife 63 having tuneable slugs 65 and solenoid 64; guard plate 49 and second fixed bottom roller 41, mounted on shaft 42 journaled in fixed bearings attached to superstructure 75.

The electronic circuitry for controlling the sequence of solenoid operation for the third and fourth folds is similar to the electronic circuitry used for the first and second folds. Anadjustable time-delay 146 controls the time delay between the third fold, actuated by solenoid driver 144, and fourth-fold solenoid driver 148 which opens solenoid 64. Optionally, an adjustable time delay 142 may be used to delay operation of both solenoid drivers 144 and 148.

The elastomeric composition comprising rollers 37, 39 and 41 is the same as the elastomeric composition used for rollers 7, 9 and 11.

, Motive power for rotation of rollers 7 and 11, illustrated in FIG. 5, is supplied by variable-speed motor 44 mounted on motor-mount86, attached to base-plate 80 to which superstructure 75 is attached. Power to notched pulley 94 on shaft 8 is transmitted from onehalf of notched double pulley 92 on shaft 50 of motor 44 by cogged timing belt 45. Similarly, power to notched pulley 96 on shaft 12 is transmitted from the other half of double pulley 92 by cogged timing belt 46.

Motive power for cross conveyor belt 22 and rollers 37 and 41, illustrated in FIGS. 5 and 6, is supplied by variable-speed motor 54, mounted on motor-mount 88, attached to base-plate 80. Power to notched pulley 78 on shaft 59 is transmitted from notched pulley 72 on shaft 51 of motor 54 by cogged timing belt 52. Similarly, power to notched pulley 82 on shaft 38 is transmitted from notched pulley 74 on motor shaft 51 by cogged timing belt 55, and power to notched pulley 84 on shaft 42 is transmitted from notched pulley 76 on motor shaft 51 by cogged timing belt 56. Notches on all pulleys have the same pitch as the cogged timing belts which engage them.

OPERATIVE EXAMPLE In a number of trial runs made on a bag-folding machine constructed according to the drawings illustrated in FIGS. 1 to 9 and described in detail above, a rate of 120 bags per minute was readily achieved, producing bags folded four times to a size of 4 X 9 /4 inches, with a machine having the following parameters.

Feed: Flat-folded refuse bags having two lengthwise accordion pleats or gussets as described above and measuring 16 X 37 inches are fed simultaneously from two bag making machines in parallel lines. The bags were fabricated from polyethylene tubing having a thickness of 1.5 mils and were heat-sealed on the leading end fed to the machine guiding trays.

Air-knives:

Length of knives 4A, 43, 24A and 24B 17 inches Length of knives 34 and 63 10.5 inches Width of air slit in air knives 0.060 inches Air pressure on air knives 40-90 psig Open time for air knife solenoids 20-60 millisec. Time delay between lst and 2nd folds 300 millisec. Rollers:

Diameter of rollers 7, 9, ll, 37, 39 and 41 4 inches Speed of rollers 7 and 9- surface it. per min. 265 Speed of rollers 37 and 4|- surface it. per min. 300 Time delay between 3rd and 4th folds I millisec.

It will be apparent to those having skill in the mechanic arts that while the air-knives described herein represent a unique contribution to the art, equivalent results may be obtained by a blow pipe, having a central feed supply of air and exit ports for the air arranged as a plurality of jets having increasingly larger diameters as one proceeds from the center to the ends. With the use of pressure sensitive transducers as described herein, the jets may be accurately reamed so as to produce a uniform pressure profile along the length of the blow-pipe. V

g It will also be apparent that other means than a light and photocell may be employed to sense passage of the unfolded article into the feed trays and trigger opening of the solenoid valves to admit high-pressure air to the air-knives. For example, a sensitive switch actuated by a feeler projecting through slots 130 and and sensitive to passage of the article over the feeler will also operate successfully.

What is claimed is:

1. A machine for imparting at least one transverse fold to a sheet, flattened bag and the like article comprising in combination:

a. a horizontal feed tray sized to accommodate said article and having a transverse slot located where a fold is desired in said article;

b. an air-knife for beginning said fold located above and aligned with said slot, said air knife comprised of an enclosure having an inlet for introducing pressurized air into said air knife and an elongated exit nozzle for emitting a jet of air into said slot, said air-knife including adjustable means for providing a uniform air-pressure profile along the exit nozzle said means for producing a uniform airpressure profile including slug means contained within said enclosure adjacent the inlet for producing turbulent air flow through the knife enclosure, said slug means having adjusting means for allowing adjustment of said slug means externally of said enclosure, said pressurized air passing through a valve prior to entering the air knife thereby allowing the pressurized air to be regulated;

roller means for completing said fold located below said feed tray for receiving said article after said air-knife forces said article through said slot including a pair of rollers having surfaces in tangential contact, said rollers comprising a fixed roller and a floating roller, said tangential surface contact being in alignment with said air-knife and said slot, said floating roller including a plurality of circumferemtial grooves and a plurality of foamed tapes attached to its circumference between said grooves, thereby preventing formation of a vacuum seal between said article and said roller;

. bias means urging said floating roller toward said fixed roller;

motor means for driving said fixed roller; photosensing trigger means responsive to the passage of said article into said feed tray to actuate said air valve, thereby admitting high-pressure air to said air-knife; whereby said sheet, flattened bag and the like article fed to said feed tray is subjected to an air-blast from said air-knife and is pushed downwardly through said slot and folded by passage between said revolving fixed and floating rollers.

7 8 7 L A machine for imparting two successive transverse a sheet, flattened bag and the like article comprising in folds to a sheet, flattened bag and the like article comcombination:

prising in combination: a. a horizontal first feed tray sized to accommodate a. a horizontal feed tray sized to accommodate said twice.

'3. A machine for imparting two successive transverse folds, followed by two successive longitudinal folds to said article and having a transverse first slot located article and having a transverse slot located where where a fold is desired in said article;

, a fold is desired in said article; b. a first air-knife'for beginning the first transverse b. a first air-knife for beginning the first fold located fold located above and aligned with said transverse above and aligned with said slot, said first air knife first slot said first air knife comprised of an enclocomprised of an enclosure having an inlet for introsure having an inlet for introducing pressurized air ducing pressurized air into said first air knife and 10 into said first air knife and an elongated exit nozzle an elongated exit nozzle for emitting a jet of air into for emitting a jet of air into said first'slot, said first said slot, said first air-knife including adjustable air-knife including adjustable means for providing mewns for providing a uniform air-pressure profile a uniform air-pressure profile along the exit nozzle, along the exit nozzle, said means for producing a said means for producing a uniform air-pressure uniform air-pressure profile including slug means profile including slug means contained within said contained within said enclosure adjacent the inlet enclosure adjacent the inlet for producing turbufor producing turbulent air flow through the first lent air flow through the first knife enclosure, said knife enclosure, said slug means having adjusting slug means having adjusting means for allowing admeans for allowing adjustment of said slug means justment of said slug means externally of said enexternally of said enclosure, said pressurized air closure, said pressurized air passing through a first passing through a first valve prior to entering the valve prior to entering the first air knife thereby alfirst air knife thereby allowing the pressurized air lowing the pressurized air to be regulated; to be regulated; c. a plurality of rollers located below said feed tray,

c. a plurality of rollers located below said feed tray, including (i) a first fixed top roller having a first including (i) a first fixed top roller having a first circumferential surface; (ii) a first floating roller cicumferential surface; (ii) a first floating roller having a second circumferential surface in tangenhaving a second circumferential surface in tangential contact with said said first surface, said tangential contact with said first surface, said tangential tial contact surface aligned with said slot and said contact surface aligned with said slot and said first air-knife, said first floating roller including a pluralair-knife, said first floating roller includingaplurality of circumferential grooves and a plurality of ity of circumferential grooves and a plurality of foamed tapes attached to its circumference befoamed tapes attached to its circumference between said grooves, thereby preventing formation tween said grooves, thereby preventing formation of a vacuum seal between said article and said rolof a vacuum seal between said article and said roller; and (iii) a first fixed bottom roller having a ler; and (iii) a first fixed bottom roller having a third circumferential surface, said third surface third circumferential surface, said third surface being in tangential contact with said second surbeing in tangential contact with said second sur face, said first fixed bottom roller including a pluface, said first fixed bottom roller including a plurality of circumferential grooves; rality of circumferential grooves; d. a second air-knife for beginning the second transd. a second air-knife for beginning the second-fold verse fold located below said first fixed top roller located below said first fixed top roller in alignment in alignment with the line of contact between said with the line of contact between said first floating first floating roller and said first fixed bottom rolroller and said first fixed bottom roller, said second ler, said second air-knife including adjustable air-knife including adjustable means for providing means for providing a uniform pressure profile a uniform pressure profile along its length and conalong its length and connected to a source of highnected to a source of high-pressure air through a pressure air through a second valve, said uniform second valve, said uniform pressure profile created pressure profile created by adjustable slugs extendby adjustable slugs extending into the interior of ing into the interior said second knife near the air said second knife near the air inlet thereto; inlet thereto;

e. bias means urging said first floating roller toward e. bias means urging said first floating roller toward said first fixed top roller and said first fixed bottom said first fixed top roller and said first fixed bottom roller; roller;

f. motor means for revolving said first fixed top roller f. motor means for revolving said first fixed top roiler and. said first fixed bottom roller; and said first fixed bottom roller;

g. photosensing trigger means responsive to the pasg. photosensing trigger means responsive to the passage of said article into said feed tray to actuate sage of said article into said feed tray to actuate said first air valve to admit high-pressure air to said said first air valve to admit high-pressure air to said first air-knife, said trigger means including an adfirst air-knife, said trigger means including an adjustable electrical time-delay to actuate said secjustable electrical time-delay to actuate said second air valve to admit high-pressure air to said second air valve to admit high-pressure air to said second air-knife subsequent to the activation of aid ond air-knife subsequent to the activation of said first air-knife; whereby said sheet, flattened bag first air-knife; and the like article fed to said feed tray is folded h. a first pair of journaled countershafts, comprising an upper countershaft and a lower countershaft; i. bias means urging said upper countershaft away from said first floating roller;

1. cross conveyor belt means for transporting twice transverse folded articles in longitudinal attitude to a second feed tray sized to accommodate said twice-folded articles, said second feed tray having a second transverse slot located where a fold is desired in said article;

k. third and fourth tuneable air-knives connected to high-pressure air through third and fourth valves, three rollers comprising a second fixed top roller, a second floating roller and a second fixed bottom roller, said rollers having tangential surface contact;

. bias means urging said second floating roller toward said second fixed top roller and said second fixed bottom roller;

m. motor means for moving said cross-conveyor belt in a direction toward said second feed tray and revolving said second fixed top roller and said second fixed bottom roller;

n. photosensing trigger means responsive to the passage of said twice-folded article from said crossconveyor belt to said second feed tray to actuate said third air valve to admit high-pressure air to said air-knife, said trigger means including an adjustable electrical time-delay to actuate said fourth air valve to admit high-pressure air to said fourth air-knife subsequent to the activation of said first air-knife; whereby said sheet, flattened bag and the like article is folded.

4. Machine according to claim 3 wherein two first feed trays in parallel alignment comprising a proximal first feed tray and a distal first feed tray, said feed trays being proximal and disstal to said second feed tray, discharge upon said cross-conveyor belt a pair of twicefolded articles, including a retarding plate bridging said conveyor belt under the discharge from said distal first feed tray, said retarding plate being movable toward and away from said second feed tray, whereby the contact of said twice-folded article from said distal feed tray with said conveyor belt may be varied so that twice-folded articles from said proximal and said distal feed trays may proceed in series to said second feed tray for their third and fourth folds. 

1. A machine for imparting at least one transverse fold to a sheet, flattened bag and the like article comprising in combination: a. a horizontal feed tray sized to accommodate said article and having a transverse slot located where a fold is desired in said article; b. an air-knife for beginning said fold located above and aligned with said slot, said air knife comprised of an enclosure having an inlet for introducing pressurized air into said air knife and an elongated exit nozzle for emitting a jet of air into said slot, said air-knife including adjustable means for providing a uniform air-pressure profile along the exit nozzle said means for producing a uniform air-presSure profile including slug means contained within said enclosure adjacent the inlet for producing turbulent air flow through the knife enclosure, said slug means having adjusting means for allowing adjustment of said slug means externally of said enclosure, said pressurized air passing through a valve prior to entering the air knife thereby allowing the pressurized air to be regulated; c. roller means for completing said fold located below said feed tray for receiving said article after said air-knife forces said article through said slot including a pair of rollers having surfaces in tangential contact, said rollers comprising a fixed roller and a floating roller, said tangential surface contact being in alignment with said air-knife and said slot, said floating roller including a plurality of circumferemtial grooves and a plurality of foamed tapes attached to its circumference between said grooves, thereby preventing formation of a vacuum seal between said article and said roller; d. bias means urging said floating roller toward said fixed roller; e. motor means for driving said fixed roller; f. photosensing trigger means responsive to the passage of said article into said feed tray to actuate said air valve, thereby admitting high-pressure air to said air-knife; whereby said sheet, flattened bag and the like article fed to said feed tray is subjected to an air-blast from said air-knife and is pushed downwardly through said slot and folded by passage between said revolving fixed and floating rollers.
 2. A machine for imparting two successive transverse folds to a sheet, flattened bag and the like article comprising in combination: a. a horizontal feed tray sized to accommodate said article and having a transverse slot located where a fold is desired in said article; b. a first air-knife for beginning the first fold located above and aligned with said slot, said first air knife comprised of an enclosure having an inlet for introducing pressurized air into said first air knife and an elongated exit nozzle for emitting a jet of air into said slot, said first air-knife including adjustable mewns for providing a uniform air-pressure profile along the exit nozzle, said means for producing a uniform air-pressure profile including slug means contained within said enclosure adjacent the inlet for producing turbulent air flow through the first knife enclosure, said slug means having adjusting means for allowing adjustment of said slug means externally of said enclosure, said pressurized air passing through a first valve prior to entering the first air knife thereby allowing the pressurized air to be regulated; c. a plurality of rollers located below said feed tray, including (i) a first fixed top roller having a first cicumferential surface; (ii) a first floating roller having a second circumferential surface in tangential contact with said first surface, said tangential contact surface aligned with said slot and said first air-knife, said first floating roller including a plurality of circumferential grooves and a plurality of foamed tapes attached to its circumference between said grooves, thereby preventing formation of a vacuum seal between said article and said roller; and (iii) a first fixed bottom roller having a third circumferential surface, said third surface being in tangential contact with said second surface, said first fixed bottom roller including a plurality of circumferential grooves; d. a second air-knife for beginning the second fold located below said first fixed top roller in alignment with the line of contact between said first floating roller and said first fixed bottom roller, said second air-knife including adjustable means for providing a uniform pressure profile along its length and connected to a source of high-pressure air through a second valve, said uniform pressure profile created by adjustable slugs extending into the interior of said second knife near the air inlet thereto; e. bias means urging said first flOating roller toward said first fixed top roller and said first fixed bottom roller; f. motor means for revolving said first fixed top roller and said first fixed bottom roller; g. photosensing trigger means responsive to the passage of said article into said feed tray to actuate said first air valve to admit high-pressure air to said first air-knife, said trigger means including an adjustable electrical time-delay to actuate said second air valve to admit high-pressure air to said second air-knife subsequent to the activation of aid first air-knife; whereby said sheet, flattened bag and the like article fed to said feed tray is folded twice.
 3. A machine for imparting two successive transverse folds, followed by two successive longitudinal folds to a sheet, flattened bag and the like article comprising in combination: a. a horizontal first feed tray sized to accommodate said article and having a transverse first slot located where a fold is desired in said article; b. a first air-knife for beginning the first transverse fold located above and aligned with said transverse first slot said first air knife comprised of an enclosure having an inlet for introducing pressurized air into said first air knife and an elongated exit nozzle for emitting a jet of air into said first slot, said first air-knife including adjustable means for providing a uniform air-pressure profile along the exit nozzle, said means for producing a uniform air-pressure profile including slug means contained within said enclosure adjacent the inlet for producing turbulent air flow through the first knife enclosure, said slug means having adjusting means for allowing adjustment of said slug means externally of said enclosure, said pressurized air passing through a first valve prior to entering the first air knife thereby allowing the pressurized air to be regulated; c. a plurality of rollers located below said feed tray, including (i) a first fixed top roller having a first circumferential surface; (ii) a first floating roller having a second circumferential surface in tangential contact with said said first surface, said tangential contact surface aligned with said slot and said air-knife, said first floating roller including a plurality of circumferential grooves and a plurality of foamed tapes attached to its circumference between said grooves, thereby preventing formation of a vacuum seal between said article and said roller; and (iii) a first fixed bottom roller having a third circumferential surface, said third surface being in tangential contact with said second surface, said first fixed bottom roller including a plurality of circumferential grooves; d. a second air-knife for beginning the second transverse fold located below said first fixed top roller in alignment with the line of contact between said first floating roller and said first fixed bottom roller, said second air-knife including adjustable means for providing a uniform pressure profile along its length and connected to a source of high-pressure air through a second valve, said uniform pressure profile created by adjustable slugs extending into the interior said second knife near the air inlet thereto; e. bias means urging said first floating roller toward said first fixed top roller and said first fixed bottom roller; f. motor means for revolving said first fixed top roller and said first fixed bottom roller; g. photosensing trigger means responsive to the passage of said article into said feed tray to actuate said first air valve to admit high-pressure air to said first air-knife, said trigger means including an adjustable electrical time-delay to actuate said second air valve to admit high-pressure air to said second air-knife subsequent to the activation of said first air-knife; h. a first pair of journaled countershafts, comprising an upper countershaft and a lower countershaft; i. bias means urging said upper countershaft away from said first floating roller; j. cross conveyor belt means for transporting twice transverse folded articles in longitudinal attitude to a second feed tray sized to accommodate said twice-folded articles, said second feed tray having a second transverse slot located where a fold is desired in said article; k. third and fourth tuneable air-knives connected to high-pressure air through third and fourth valves, three rollers comprising a second fixed top roller, a second floating roller and a second fixed bottom roller, said rollers having tangential surface contact; l. bias means urging said second floating roller toward said second fixed top roller and said second fixed bottom roller; m. motor means for moving said cross-conveyor belt in a direction toward said second feed tray and revolving said second fixed top roller and said second fixed bottom roller; n. photosensing trigger means responsive to the passage of said twice-folded article from said cross-conveyor belt to said second feed tray to actuate said third air valve to admit high-pressure air to said air-knife, said trigger means including an adjustable electrical time-delay to actuate said fourth air valve to admit high-pressure air to said fourth air-knife subsequent to the activation of said first air-knife; whereby said sheet, flattened bag and the like article is folded.
 4. Machine according to claim 3 wherein two first feed trays in parallel alignment comprising a proximal first feed tray and a distal first feed tray, said feed trays being proximal and disstal to said second feed tray, discharge upon said cross-conveyor belt a pair of twice-folded articles, including a retarding plate bridging said conveyor belt under the discharge from said distal first feed tray, said retarding plate being movable toward and away from said second feed tray, whereby the contact of said twice-folded article from said distal feed tray with said conveyor belt may be varied so that twice-folded articles from said proximal and said distal feed trays may proceed in series to said second feed tray for their third and fourth folds. 